Phenotypic variability in a large Czech family with a dynamin 2-associated Charcot-Marie-Tooth neuropathy.

Mutations in the Dynamin 2 gene (DNM2) cause autosomal dominant centronuclear myopathy or autosomal dominant (AD) Charcot-Marie-Tooth (CMT) disease. Here the authors report one large Czech family with 15 members affected with an AD CMT phenotype of extraordinary variability. Genetic linkage analysis using SNP arrays revealed a locus of about 9.6 Mb on chromosome 19p13.1-13.2. In this critical interval, 373 genes were located. The only gene herein known to be associated with an intermediate type of CMT was Dynamin 2 (DNM2). Subsequent sequence analysis of the DNM2 gene in the index patient revealed a novel missense mutation p.Met580Thr. This missense mutation segregated with the neuropathy, indicating the causal character of this mutation. The phenotype of CMT in this family shows mild to moderate impairment with relatively preserved upper limbs and a very broad range of the onset of clinical symptoms from an early onset around the age of 12 to the late onset during the fifth decade. Electrophysiology showed an intermediate type of peripheral neuropathy. The motor median nerve conduction velocity varied from 36 m/s to normal values with signs of asymmetrical affection of peripheral nerves. No additional symptoms such as cranial nerve involvement, cataract, and signs of neutropenia or myopathy syndrome were observed in any member of the family yet. The progression was slow with no loss of ambulation. The authors suggest that the characterization of clinical variability in a single family may help to direct the genetic analysis directly to the rarely observed DNM2 mutations.

A 71-nucleotide deletion in the periaxin gene in a Romani patient with early-onset slowly progressive demyelinating CMT.

BACKGROUND: Mutations in the periaxin (PRX) gene cause autosomal recessive demyelinating neuropathy Charcot-Marie-Tooth (CMT) type 4F. To date, 10 non-sense or frameshift PRX mutations have been reported in patients with early-onset neuropathy and further disease course consistent with either Dejerine-Sottas neuropathy or slow-progressive demyelinating CMT. METHODS: We sequenced 59 patients from 55 Czech families including four unrelated patients of Romani (Gypsy) origin with early-onset CMT displaying decreased nerve conduction velocities. RESULTS: We identified a novel homozygous mutation c.3286_3356del71 (K1095fsX18) in one Romani patient showing very slow disease progression. Amongst non-Romani Czech CMT patients, PRX mutations have been proven to be very rare.

Laing distal myopathy with a novel mutation in exon 34 of the MYH7 gene.

We investigated a four-generation family of German ancestry with distal myopathy. Four individuals in two generations were affected. Foot and toe extensor paresis progressing very slowly over decades was the core neurological sign, reflected by fatty infiltration of the lower leg extensor muscles on muscle MRI. Additionally, finger extensor paresis was present in two patients and quadriceps muscle paresis in one. Distal sensory signs had initially given rise to the diagnosis of axonal Charcot-Marie-Tooth (CMT) disease. Two patients had extended verrucae of their foot sole, which may or may not be part of the disease spectrum. All four patients had a novel c.4645G > C mutation in exon 34 of the MYH7 gene that was not present in three clinically unaffected family members. Muscle biopsy of one patient revealed a myopathic pattern associated with type 1 muscle fibre atrophy and core-like lesions in many muscle fibres consistent with a myosin-related myopathy. We conclude that some of the typical clinical signs such as extensor weakness of the big toe and the little finger may only develop in the further course of the disease.

Novel EGR2 mutation R359Q is associated with CMT type 1 and progressive scoliosis.

Mutations in the early growth response 2 gene (EGR2) cause demyelinating neuropathies differing in severity and age of onset. We tested 46 unrelated Czech patients with dominant or sporadic demyelinating CMT neuropathy for mutations in the EGR2 gene. One novel de-novo mutation (Arg359Gln, R359Q) was identified in heterozygous state in a patient with a typical CMT1 phenotype, progressive moderate thoracolumbar scoliosis and without clinical signs of cranial nerve dysfunction. This patient is presently less affected compared to previously described Dejerine-Sottas neuropathy (DSN) patients carrying another substitution at codon 359 (Arg359Trp, R359W). This report shows that EGR2 mutations are rare in Czech patients with demyelinating type of CMT and suggests that different substitutions at codon 359 of EGR2 can cause significantly different phenotypes.

Clinical and morphological phenotype of HMSN 1A mosaicism.

Clinical, neurophysiological and morphological studies on a patient with mosaicism of the 17p11.2 duplication were performed in detail for the first time. Since duplication occurs during paternal meiosis, a somatic reversion is suggested, leading to mosaicism. The proportion of nuclei with duplication varied markedly between 49% in blood cells and 74% in tissue from the sural nerve. Clinically, mild symptoms of a motor and sensory neuropathy were present. However, neurophysiological changes and findings in the sural nerve biopsy were consistent with a typical hereditary motor and sensory neuropathy type 1 (HMSN 1). Differing clinical findings in patients with mosaicism of the 17p11.2 duplication may be explained by a varying degree and/or time of reversion.

The peripheral myelin protein 22 kDa (PMP22) gene is amplified in cell lines derived from glioma and osteogenic sarcoma.

Two glioma (SF188, SF763) and two osteogenic sarcoma cell lines (RH30, SA1) were examined for the presence of an amplification of the PMP22 gene by means of fluorescence in situ hybridization (FISH). In one cell line of both cell types, we found about 10 copies of the PMP22 (peripheral myelin protein 22 kDa) gene, located on different marker chromosomes within homogeneously staining regions. Surrounding chromosome 17p material was found to be coamplified, but coamplification of TP53 (17p13) and erbB2/Her2 (17q11.12) were excluded by FISH for both cell lines, SF763 and RH30. This is the first report of a PMP22 amplification in cell lines derived from human tumors.

PMP22 Thr118Met is not a clinically relevant CMT1 marker.

It is controversial if peripheral myelin protein 22 gene (PMP22) Thr118Met represents a functionally irrelevant polymorphism or, since hemizygosity for this variant has been found in two patients with Charcot-Marie-Tooth disease type 1 (CMT1 patients), it can act as a recessive CMT1 mutation. To shed further light on this variant and its diagnostic value we searched for carriers in 1018 individuals from the German general population, in 104 probands with hereditary neuropathy with liability to pressure palsies (HNPP) who were carriers of the 1.5-Mb deletion frequently associated with this disorder, in 187 patients with the 1.5-Mb duplication, and in 22 patients with a CMT1 phenotype who did not have any detectable anomaly in the PMP22 gene. Using allele-specific PCR we identified 14 [allele frequency (AF)=0.007] in the German general population, one (AF=0.01) in the HNPP group and six (AF=0.016) and two (AF=0.05) carriers of the PMP22 Thr118Met mutation in the CMT1 groups with and without gene defect. Carriers from all groups showed nerve conduction velocities which did not differ from typical values for these groups. We conclude that the hemizygous occurrence of the 118Met allele does not usually cause CMT1. Because of previous reports on its association with disease, and because its allele product shows abnormalities in in vitro expression systems, it seems possible that this mutation, together with yet unidentified factors, predisposes to CMT1. Alternatively, previously reported disease associations occurred by chance, and the 118Met allele causes biochemical abnormalities irrelevant for CMT1 formation. In either case this mutation is not a clinically relevant disease marker.

A polymorphic locus in the intron 16 of the human angiotensin-converting enzyme (ACE) gene is not correlated with complex regional pain syndrome I (CRPS I).

Exaggerated neurogenic inflammation has been recognized to be one reason for many CRPS symptoms. Since angiotensin-converting enzyme (ACE) is a key enzyme for the termination of neurogenic inflammation, it has been selected as a candidate gene for CRPS predisposition. A previous report of an insertion/deletion (I/D) polymorphism in intron 16 within the ACE gene implicated an increased risk to develop CRPS I associated with the D allele. However, in the present study the D allele frequency was not increased in CRPS I cases (0.51 for D allele, 0.49 for I allele). Furthermore, there was no co-segregation of any genotype (DD, ID, II) with the CRPS phenotype in 12 selected familial CRPS I cases from six CRPS I families. In conclusion, the results presented herein render this particular ACE gene polymorphism unlikely to be a predisposing factor for CRPS I.

Transcriptional startpoints and methylation patterns in the PMP22 promoters of peripheral nerve, leukocytes and tumor cell lines.

PMP22 is a dosage sensitive gene responsible for Charcot-Marie-Tooth type 1A (CMT1A) neuropathy and hereditary neuropathy with liability to pressure palsies (HNPP). PMP22 is expressed in myelinating Schwann cells in the peripheral nerve, but also in a variety of other tissues. PMP22 expression is regulated by alternatively used promoters, the relative expression of the different PMP22 transcripts is tissue-specific. At first we analysed the transcriptional startpoints of the different PMP22 transcripts. Transcript 1A starts from a distinct nucleotide, whereas transcript 1B and the here described transcript 1C revealed multiple transcriptional startpoints in sciatic nerve as well as in the osteosarcoma and glioblastoma cell lines, RH30 and SF763. Using promoter specific primers we identified transcripts from each of the three promoters in sciatic nerve and RH30, whereas transcript 1B is absent in SF763. Leukocytes do not express PMP22 at all. Additionally, we determined the methylation pattern of CpG islands present in the PMP22 promoters 1B and 1C for leukocytes, sciatic nerve, SF763 and RH30, the latter carrying multiple copies of the PMP22 gene. We observed that there was no methylation in promoter 1B and 1C in sciatic nerve and leukocytes. However, hypermethylation of promoter 1B was discovered in SF763 and indicates a silencing effect. In RH30 most copies of promoters 1B and 1C were methylated but the few remaining hypomethylated copies were sufficient for strong expression of PMP22. These results indicate that the transcriptional control in tumor cell lines is probably different from leukocytes and sciatic nerve.

Autosomal dominant Charcot-Marie-Tooth disease type 1A and hereditary neuropathy with liability to pressure palsies: detection of the recombination in Slovene patients and exclusion of the potentially recessive Thr118Met PMP22 point mutation.

Charcot-Marie-Tooth disease type 1 (CMT1) and hereditary neuropathy with liability to pressure palsies (HNPP) are the most frequent autosomal dominantly inherited disorders of the peripheral nervous system. The recessive inheritance is observed only exceptionally. Unequal crossing-over of misaligned flanking CMT1A-REP elements on chromosome 17p11.2 is the most frequent cause of the CMT1A duplication and of the reciprocal deletion in HNPP patients. Recently a recombination was noted. In our study 71 Slovene CMT1 patients from 36 families, 12 HNPP patients from 6 families and their 31 healthy relatives were analysed for the presence of these recombination mutations. In 29 of 36 unrelated CMT1 (81%) and in all 6 unrelated HNPP patients the duplication or the deletion, on chromosome 17p11.2-12 was detected. In 26 out of 29 duplication patients (CMT1A) (90%) a 3.2 kb EcoRI/SacI duplication junction fragment was observed. The analogous 7.8 kb EcoRI/EcoRI deletion junction fragment was found in 4 out of 6 unrelated HNPP deletion patients (67%). Overall we found a recombination mutation inside the in 86% of unrelated Slovene CMT1A and HNPP patients. One hundred and thirty-six DNA samples of the CMT1 and HNPP patients and of the healthy controls were negative for the potentially recessive Thr118Met PMP22 amino acid substitution. Dominantly inherited CMT1A duplications and HNPP deletions on chromosome 17p11.2 are thus, as in most other European countries, the most common mutations in Slovene CMT1 and HNPP patients. No signs of polymorphism or of potentially recessive mutation were found at the specific Thr118Met PMP22 site.

Charcot-Marie-Tooth disease type 1A (CMT1A) and hereditary neuropathy with liability to pressure palsies (HNPP): reliable detection of the CMT1A duplication and HNPP deletion using 8 microsatellite markers in 2 multiplex PCRs.

Charcot-Marie-Tooth disease (CMT) and hereditary neuropathy with liability to pressure palsies (HNPP) are the most frequent inherited disorders of the peripheral nervous system. They are clinically and genetically heterogeneous. A submicroscopic tandem duplication of 1. 5 Mb in chromosome 17p11.2-12 comprising the PMP22 gene is found in 70.7% of autosomal dominant Charcot-Marie-Tooth type 1 (CMT1) patients. A reciprocal deletion is found in 87.6% of HNPP patients. The size of the typical CMT1A duplication is too small for classical cytogenetics and the whole region including the CMT1A-REP elements is sometimes too complex for a single DNA analysis method. We present results of a multiplex PCR of 8 microsatellite markers with multicolour fluorescence primer labelling followed by fragment analysis on an ABI 310 Prism analyzer to simplify the diagnostic procedure. Results for 24 patients can be obtained within 24 h. This method was applied on 92 DNA samples of unrelated patients carrying a typical CMT1A duplication previously confirmed by two colour fluorescence in situ hybridization (FISH, probe c132G8) and EcoRI/SacI Southern blotting (probe pLR7.8). Three alleles of three different sizes were clearly detected at least once in 88 of them (95.6%). Subsequently this analysis was applied on 312 Czech patients and revealed a CMT1A/HNPP rearrangement in 109 out of them.

Mosaicism for Charcot-Marie-Tooth disease type 1A: onset in childhood suggests somatic reversion in early developmental stages.

A 1.5 Mb duplication on chromosome 17p11.2 is typical for the great majority of patients suffering from Charcot-Marie-Tooth type 1A (CMT1A) disease. A female child of 4 years with clinical signs and symptoms of a demyelinating neuropathy was examined for the presence of this duplication. Analysis of MspI polymorphisms in DNA extracted from peripheral blood failed due to homozygosity for probes pVAW409R3a and pEW401HE. Also, no EcoRI/SacI 3.2 kb junction fragment or dosage difference with probe pLR7.8, characteristic of the CMT1A duplication, was found. However, fluorescence in situ hybridization (FISH) analysis with the PMP22 specific probe c132G8 revealed in peripheral blood lymphocytes 60% of interphase nuclei with CMT1A duplication indicating the probability of mosaicism. In interphase nuclei extracted from nerve tissue the duplication was detectable in 88%, in muscle tissue in 72% of the analyzed nuclei. This suggests the presence of a somatic CMT1A duplication mosaicism that can only be reliably detected by FISH. The early onset and severity of the phenotype indicates that the hypothesized somatic reversion is probably fixed to early developmental stages.

A GLC1A gene Gln368Stop mutation in a patient with normal-tension open-angle glaucoma.

PURPOSE: To present a case involving a patient with normal-tension glaucoma with a Gln368Stop mutation of the myocilin/trabecular meshwork inducible glucocorticoid response protein (MYOC/TIGR) gene. METHODS: Slit-lamp biomicroscopic and gonioscopic examination, morphometry of the optic disc, 24-hour intraocular pressure (IOP) profile, and perimetry were performed to determine the phenotype of the patient. Neurologic examination and a computed tomographic (CT) scan of the brain were performed to rule out a neurologic disorder. Single-strand confirmation polymorphism (SSCP) analysis and subsequent sequence analysis of blood was performed for genotyping of the GLC1A gene. RESULTS: A nonsense codon, namely a Gln368Stop mutation in the third exon of the GLC1A gene, was found in this patient with normal-tension glaucoma. CONCLUSION: In contrast to previous reports, a Gln368Stop mutation of the GLC1A gene need not be confined to patients with glaucomatous optic atrophy due to high IOP. The pathogenesis of glaucoma associated with GLC1A gene mutations might be more complex than expected, and (unknown) suppressor mechanisms have to be considered.

Primary congenital glaucoma: three case reports on novel mutations and combinations of mutations in the GLC3A (CYP1B1) gene.

PURPOSE: To describe three patients with congenital glaucoma homozygous and compound heterozygous for different mutations and benign sequence variants in the cytochrome P 450 1B1 (CYP1B1) gene. METHODS: All patients were examined by slit-lamp biomicroscopy, gonioscopy, measurement of the cornea and optic disc, ultrasound biometry, and automated static threshold perimetry when possible. Direct sequence analysis was performed on DNA extracted from peripheral blood from the patients and their parents. RESULTS: For patient 1, a newborn boy with buphthalmos and an opaque cornea, a novel homozygous C/T transition in codon 355 (CGA>TGA) led to a predicted nonsense codon Arg355X truncating the protein by 188 amino acids. For patient 2, a 24-year-old man, a compound heterozygous mutation 1410-1422del/1546-1555dup was found. For patient 3, a 34-year-old man, two novel heterozygous missense mutations resulting in an Ala443Gly and a Glu229Lys amino acid exchange and five benign sequence variants were found. CONCLUSION: Our results confirm the crucial role of CYP1B1 mutations for congenital glaucoma.

A novel mutation in CACNA1A associated with hemiplegic migraine, cerebellar dysfunction and late-onset cognitive decline.

Hemiplegic migraine (HM) is a rare and severe subtype of migraine with aura, characterized by some degree of hemiparesis and other aura symptoms. Mutations in three genes (CACNA1A, ATP1A2 and SCN1A) have been detected in familial and, more rarely, in sporadic cases. The disease can be complicated by permanent neurological deficits, the most frequent one being a cerebellar syndrome; in addition, mental retardation has been recognized as part of the phenotypic spectrum. Here, we report a Caucasian male with a novel CACNA1A mutation and an unusual clinical phenotype: the patient, who had had a history of only two HM attacks, sought medical advice at age 49 primarily because of increasing cognitive decline accompanied by cerebellar dysfunction. While common neurodegenerative causes were excluded, neuropsychological evaluation revealed a distinct profile of deficits of a subcortico-prefrontal type as previously reported in patients with cerebellar dysfunction. This suggests a possible causal link between cerebellar and cognitive disturbances in this patient; in addition to these pathophysiological aspects, we review of the role of the cerebellum in cognition.

Severe Myoclonic Epilepsy in Infancy - Adult Phenotype with Bradykinesia, Hypomimia, and Perseverative Behavior: Report of Five Cases.

Dravet syndrome or severe myoclonic epilepsy in infancy (SMEI) is an epileptic syndrome characterised by refractory epilepsy and intellectual disability, typically presenting with febrile and afebrile generalised and unilateral clonic/tonic-clonic seizures in the first year of life and other types of seizures appearing later in the course of the disease. Five adult patients with SMEI and SCN1A mutations are reported, in which motor and behavioural abnormalities were outstanding symptoms. Bradykinesia, responding with latency, slow speaking with a thin voice, midface hypomimia and perseveration were distinctive features in all cases. These symptoms may be fit to define the adult phenotype of SMEI beyond seizure/epilepsy criteria. The motor and behavioural symptoms are discussed in the context of a possibly underlying frontal lobe/mesofrontal and cerebellar dysfunction.